Stretchable textiles produced from the back-twisting of highly swollen cellulosic yarns



r 3,403,504 I Patented Oct. 1, 196 8 STRETCHABLE TEXTILES PRODUCED FROM THE BACK-TWISTING OF HIGHLY SWOLLEN CELLU- LOSIC YARNS Carl Hamalainen, Metairie, Hubert H. St. Mard, New

Orleans, and Albert S; Cooper, Jr., Metairie, La., assignors to the United States of America as represented by the Secretary of Agriculture N Drawing. Filed July 13, 1966, Ser. No. 564,735

, 5 Claims. (Cl. 57-464) ABSTRACT OF THE DISCLOSURE A process which involves swelling cellulosic yarns either slack or under tension, both of normal and of high twist construction; washing and drying the yarns, to set the configuration; and backtwisting the yarns thereby producing stretch yarns which may be woven to produce fabrics with excellent stretch properties.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America This invention relates to the production of stretch textile material by swelling either slack or under tension cellulosic yarns of normaland high-twist construction followed by backtwisting to produce stretch yarns and then weaving the resultant yarns'into"fab1ic to producefabric with stretch properties.

Most stretch cotton fabrics are going into apparel slacks, blouses, pajamas, uniforms for waitresses and nurses, and other garments'but'upholstery and slipcover fabrics are also being made. Stretch adds comfort and allows the fabric to give at knees and elbows without unsightly bagging.

Stretch yarns have been produced by treating highly twisted yarns with crosslinking agents, heat curing them in this highly twisted state and then backtwisting beyond the neutral ply twist. Stretch has also been obtained by shrinking the yarn about 40 to 70% by tensionless mercerization followed by subsequent washing and drying without restretching the yarn. Highly chemically modified yarns, such as acetylated yarns,'have been heat set fol lowed by twisting techniques to produce stretch. This copiending application Ser. No. 564,759 filed of even date,

entitled Cotton Stretch Yarn by Graft. Polymerization f VinylMonomers Followedby Backtwisting or Falsetwisting.

Tensionless mercerization procedures produce stretch in yarn by virtue of its shrinkage effects. This is the basis for the slack mercerizing process for producing stretch.

Mercerization causes a great deal of swelling in cellulosic fibers with concomitant disruption of hydrogen bonds. These bonds are reestablished in new positions after swelling, washing, and drying procedures. Disrupting the geometry of these highly swollen yarns as by backtwisting, results in a coiled or crimped structure with stretch properties.

For the practice of this invention, various conditions for swelling may be employed. Swelling may be carried out slack without any tension or it may be carried out with sufficient tension to prevent any shrinkage of the yarns being treated, or it can be swollen wit-h a greater amount of tension to stretch the yarns during treatment. In this practice of the invention, we have retained the original length of the yarn skeins during swelling under tension. Swelling may be carried out in any caustic solution of suitable strength. We prefer the use of caustic solution of about 23% sodium hydroxide. A wetting agent, such as 1% Dypenol, is generally employed, although any other suitable wetting agent may be used and the swelling can also be effected without a wetting agent. An added swelling agent, such as sodium thiocyanate, may be used to enhance the swelling of the cellulose in the caustic.

Although any temperature in which effective swelling may be accomplished can be used, in the practice of the present invention we chose ambient room temperature of about 25 C. and an elevated temperature of about 92 C.

In the practice of the present invention, the highly swollen yarns were prepared from scoured and bleached 24/2 cotton yarn, the normal singles twist being 4TM-Z, and the ply twist 4TMS. The high-twist yarn had 4TM-Z single twist and 7TMZ ply twist construction. This does not preclude that othertwist multiples or constructions to effect adequate swelling.

(b) Washing, drying, scouring, and washing and drying in the ordinary manner;

(c) Back-twisting the treated yarn; and

(d) Allowing the back-twisted yarn to relax in water.

The process can be varied to include yarns of hightwist construction and/or while varying the tension during the wetting step (a).

In order that the concept of the invention may be more fully understood, the following examples are set forth primarily for the purpose of illustration and any specific enumeration of detail contained therein should not be interpreted as a limitation of the case, exceptas indicated in the appended claims.

EXAMPLE 1 Bleached and scoured 24/2 normal-twist cotton yarns of 4TM-Z singles and 4TM-S ply twist construction were skeined into 500 yard skeins. Six SOD-yard skeins were treated in 23% sodium hydroxide solution containing 1% Dypenol wetting agent under each of the conditions listed for mercerization. The single fiber properties (as obtained on the Uster Automatic Single Yarn Tester) of the unrelaxed yarns after they had been washed, dried, and backtwisted 8TM in the Z direction are shown in Table 1.

There is an improvement in elongation and breaking strength in the unrelaxed single yarn. 11

EXAMPLE 2 The yarns prepared in Example 1 were woven into fabric using them as filling yarns only with 40 picks per inch filling. The fabric was relaxed in hot water and dried. The stretch properties of these fabrics are shown in Table 2. There is a considerable increase in the amount of elongation at break of the one-inch strip fabric and excellent stretch and recovery of the two-inch strips after 5 cyclic loadings with 2-lb. load.

TABLE 2 1 inch strip 2 inch strip, 5 cycles, 2-11). load 4 f 7 Recovery Mercerizing conditions 13.8., Elong., Stretch, Growth, percent at 24 hr., 1

lbs. percent percent percent 1 min. 24 hr.

50. 4 110 62 13. 8 10.0 84 58.3 132 63 16.0 t 12.2 80 46. 8 112 65 16. 6 12, 6 81 54. 5 129 62 16. 4 13. 79 Tension, 92 0.,

(7%) 47. 8 111 66 16. 4 12. 7 81 Slack, 92 0., 60 m 55. 0 129 65 16.8 13. 1 80 Untreated control 51. 22 10 1. 4 1.1 89

TABLE 3 Mercerizing conditions Breaking Elonga- Tex. No.

load, gm. tion, percent Tension, 25 0., 15 min. 636 7.8 48.3 Slack, 25 C 15 min. 665 9. 3 50.1 Tension, 92 0., 60 mi 615 8. 0 48. 4 Slack, 92 0., 60 min 630 10. 6 49.3 Tension, 92 0., 60 m 1., NaSCN (7 630 0 4B. 1 Slack, 92 0., 60 min., NaS ON (7 647 '9. 5 52.1 Untreated control 660 7. 6 4 48. 1

EXAMPLE 3 Bleached and scoured 24/2 high twist cotton yarn of 4TM-Z, singles and 7TM-Z ply twist construction were skeined into 500 yard skeins. Six-500 yard skeins were The elongation and strength of the high twist yarns alter baektwistllig was not as high as that of the normal-twist yarn.

TABLE 4 1 inch strip 2 inch strip, 5 cycles, 2-lb. load Recovery Mercerizing conditions 13.8., lb. Elong., Stretch, Growth, percent 24 hr.,

percent percent percent 1 min. 24 hr. i

T nsion, 25 0., 15 min 45.9 34 7.3 4.6' 86 Slick, 25 0., 15 min 43.8 36 7. 3 5.2 85 Tension, 92 0., 60 min. 41. 9 60 37 6. 7 4. 7 84 Slack, 92 0., 60 min 41. 6 66 37 7. 2 5.1 86

2 0., O N ii r fii f .fjfi i nln 37. 2 51 a4 5. 9 3.9 so Slack, 92 0., 60 min NaSC 41.4 62 36 5.9 4.2' 86 Untreated control 51. 5 22 10 1. 4 1.1 89

60 We claim:

treated in 23% sodium hydroxide solution containing 1% Dypenol wetting agent under each of the conditions listed for mercerization. The single yarn properties (as obtained on the .Uster Automatic Since Yarn Tester) of the unrelaxed yarns after they had been washed, dried, and backtwisted 15TM in the S direction are shown in Table 3.

EXAMPLE 4 The yarns prepared in Example 3 were woven into fabric using them as filling yarns only with 40 picks per inch filling. The fabric wasrelaxed in hot water and dried. The stretch properties of these fabrics are shown in Table 4. These fabrics show excellent elongation at break of the 1 inch strips and high stretch values in the 2 inch strips. The recovery from stretch after 24 hours relaxation is good.

1. A process for imparting improved stretch properties to a cellulosic yarn comprising w h (a) wetting a cellulosic yarn of normal-twist or h ightwist construction, while said yarn is under no tension or under a tension just suificient to maintain its length constant, with an aqueous solution containing about 23% by weight of sodium hydroxide and about 1% by weight of a wetting agent compatible with the said 23% sodium hydroxide solution, about from-25 to 92 C. for a periodof time of about frorrrlS .to

- 60 minutes,'to swell the yarn; 4.

(b) washing, drying, scoring, and .washingiandtdrying the swollen yarn of step (a); -1 a (c) back-twisting the dried yarn of step .(b); and.

5 6 (d) allowing the back-twisted yarn of step (c) to relax yarn in step (a) is carried out while the yarn is under a in water. tension just sufficient to maintain its length constant.

2. The process of claim 1 wherein the cellulosic yarn is of normal-twist construction. References Cited 3. The process of claim 1 wherein the cellulosic yarn is 5 UNITED STATES PATENTS of high-twist construction.

4. The process of claim 1 wherein the wetting of the 555332 22; a] t e rfs io g Step (a) Is Carrled out Whlle the y 15 under no Cooper et a]I 5. The process of claim 1 wherein the wetting of the 10 JOHN PETRAKES, Primary Examiner. 

